Talk:Heat engine

difference between Cycle type and engines

The difference between Cycle type and engines needs to be split apart. The Diesil cycle can be run completely differently from the diesil engine. Ericsson created a Diesil cycle engine that ran on external combustion. The diesil cycle doesn't require diesil fuel and can have an air fuel mixture instead of fuel injection. The Otto Cycle can be either 2 or 4 stroke.Eric Norby

Would it be reasonable to add the tropical cyclone as another example of a heat engine? Presumably under the vapor power cycle heading.

Cyclones: I'm not an expert on cyclones, but I would guess it is roughly an example of one of the types already mentioned? If anyone knows more about it, it's a good example to add. Mat-C 17:40, 10 July 2005 (UTC)

Changed: moved carnot out of vapour cycle. Nothing about carnot is specifically phase change that I know of (and nothing on its page suggests so).Mat-C 17:40, 10 July 2005 (UTC)

I've removed this from the Ericsson Cycle page, would be nice to include something like it here: Thermodynamically, the Ericsson cycle is more similar to the Stirling and Carnot cycles. All use isothermal compression and expansion at the hot and cold temperatures. To transition the gas between the hot and cold temperatures Carnot uses adiabatic compression and expansion, Stirling uses constant volume regeneration, and Ericsson uses constant pressure regeneration. All are theoretically capable of Carnot efficiency if there are no losses. Both Brayton and Ericsson can be realized by the same simple machine, a turbine compander. A Brayton cycle with regeneration and an infinite number of stages of intercooling and reheat is equivalent to the Ericsson cycle. Mat-C 18:08, 12 July 2005 (UTC)

What is the purpose of this page?

This page appears to be a mishmash of highly technical discussion and lists. The lists are incomplete and the technical discussion is mostly covered more usefully in other articles (such as carnot cycle). Would it be best to make this page a simple description with suitable off links to more detail; should we try to make the list complete; is it useful to have diagrams?

The article doesn't make the relationship between heat engines and heat pumps clear, and it doesn't make the point that all (almost?) energy transformations involve the carnot efficiency (e.g. batteries, solar panels, lights).

I'm happy to spend a while cleaning it up, but I am not getting an feeling for what really belongs here. njh 08:36, 4 February 2006 (UTC)

Agree - need for an overhaul

Nathan - I agree with your comments about this page. I would propose a reasonable simple explanation of what a heat engine is, and relationship to a heat pump. This article might refer to heat/work cycles in nature but I think the emphasis should be on man-made machines. It would be good to have list of links to cycles, and also to pages referring to example machines. Agree that it would be best to keep cycles and machines separate.

It would be great if this article could also be mirrored for heat pumps, which is also in need of some attention. mike 17:45, 17 March 2006 (UTC)

removed 'photon cycle'

I removed "photon cycle" and the only example listed under it, solar sail. A solar sail operates by converting radiation pressure into mechanical energy. That makes it a type of engine other than a heat engine. --Delirium 06:30, 10 September 2006 (UTC)

reference to new article: Heat engine classifications

I created a new article with the goal to develop a basic list that is logical, conceptually clear, and inclusive of all practicable approaches to building a machine to convert heat energy into mechanical energy. KYcrank 00:32, 6 November 2006 (UTC)

I would like to know more about that type of convertion(heat to mech),so where can I find this article of yours?? TUCSES (talk) 10:31, 20 September 2016 (UTC)

KYcrank appears to have been referring to material now found in the article Timeline of heat engine technology. Dolphin (t) 11:07, 20 September 2016 (UTC)

Agree with first two comments - This article is poor

I've been interested in heat engines for some time, and I have never heard anyone make the argument (especially after just having pointed out that heat engines work on a heat differential, and extract power from that differential alone) that internal combustion engines are heat engines of any kind-- steam, gasoline, diesel... These engines are, by no possible stretch of definitions I can think of, operating by differential in heat. I was writing in here several examples of why it's past ridiculous to include many of these engine types as heat engines, but it's not even worth doing: the statement itself is self-evidently ludicrous. 68.99.213.231 05:05, 4 January 2007 (UTC) Andy R.

New heat engine model should be incorporated

There is a new paper published in the "International Journal of Energy Research" (http://dx.doi.org/10.1002/er.1312) that details a new heat engine model that accurately reproduces the efficiencies of Otto, Brayton, and Stirling cycle engines. This new model should be covered under this topic. —The preceding unsigned comment was added by 69.244.46.21 (talk) 14:18, 7 March 2007 (UTC).

I hacked this discussion from the middle of the article Ϙ 18:49, 4 June 2007 (UTC). [-->I think this section needs correction. MIT's Professor Gyftopoulos seems pretty smart: http://web.mit.edu/nse/people/faculty/gyftopoulos.html

He slams the endoreversible theory in a paper titled: "On the Curzon–Ahlborn efficiency and its lack of connection to power producing processes".

Abstract: "Because some physicists continue to defend the nonexistent theory of finite time thermodynamics, additional incontrovertible experimental and theoretical evidence is provided about its irrationality and nonreality."

Curzon-Ahlborn efficiency is the endoreversible theory. ---Steve]

>The Carnot Cycle limit cannot be reached with any gas-based cycle, but engineers have worked out at least two ways to possibly go around that limit

Helllooo, nurse... Either very poor choice of wording or suggestion that those engineers are trying to exceed Carnot cycle efficiency limit. THAT I sorta would like to see, coz it's pretty equivalent to creating perpetuum mobile. Except not going to happen. —Preceding unsigned comment added by 87.110.96.68 (talk) 23:01, 14 March 2008 (UTC)

Athermal engines efficiency （Yu，Deng Hai，热效率趋向100%的能量利用新途径I:从无序到有序，中国工程热物理学会，工程热力学与能源利用学术会议，1994；

Deng Yu，Deng Hai，邓宇，邓海，热效率趋向100%的能量利用新途径II:量子化内能的分解及有序化的演变，中国工程热物理学会，工程热力学与能源利用学术会议，1994）

Efficiency

I came to this page hoping to find information about the efficiency of engines, but just a couple scattered references. That would be a useful list, although I am sure it is hard to get consistent information.

Also, you might mention rocket engines in the article. They may be the most efficient heat engines, up around 65%. DonPMitchell (talk) 17:54, 29 June 2008 (UTC)

A rocket motor is not a heat engine. Mass crosses the system boundary. Globbet (talk) 20:01, 22 August 2008 (UTC)

But under the steady flow assumption (see below) they can be treated as heat engines, and described using the Brayton cycle. —Preceding unsigned comment added by 88.18.219.135 (talk) 10:35, 9 May 2009 (UTC)

The first sentence of this section contains an error: "The efficiency of a heat engine relates how much useful power is output for a given amount of heat energy input." The word "power" should be replaced by "work" or "energy", because power = energy per unit time, and "work" is a synonym for "energy" in the technical physic jargon. I'm replacing "power" with "work". DavidMCEddy (talk) 14:36, 5 June 2010 (UTC)

Athermal engines efficiency 100%

The efficiency of traditional heat engines is a limit 1/3， 33.33%.

Px=Py=Pz=P,

PV=(2/3)NEk =(1/3)mv²N

when 3-Dimension

V²=Vx²+Vy²+Vz²

when 1-D in 3-Dimension

Vx²=3Vx²=3v²=V²

PxV=(1/3)mV²N=(1/3)mVx²N

=(1/3)m3Vx²N

=mVx²N

=2EKN

Px>P

Px=3P=3NRT/V

ηs=A/Q=1 -(T2/T1)

=1 -(T2/Q1)S

entropy S→0, so

(T2/Q1)S→0,

ηs→1

0≤η<<1

Q=3PV

or

Q=U=3PV

η0=A/Q=PV/3PV

=1/3

A=3PV

ηs=A/Q=3PV/3PV

=1

An athermal heat engine is a contradiction in terms, and many heat engines exceed 33% efficiency; so I've deleted, what appears to me to be, OR.Teapeat (talk) 01:43, 22 April 2012 (UTC)

References

Internal combustion engines can't be considered heat engines

From the definitions of heat engines that I have seen, I don't believe that internal combustion engines can be considered heat engines. This is because the input is chemical energy. This chemical energy is turned into heat internally and this heat is then turned into mechanical energy. However, the input to the engine is chemical and not heat. —Preceding unsigned comment added by PhillyPhysics (talk • contribs) 16:51, 26 July 2008 (UTC)

Comment: Internal Combustion Engines are heat engines - User:Twingy

Correct: an internal combustion engine is not a heat engine. Mass crosses the system boundary. Globbet (talk) 20:03, 22 August 2008 (UTC)

Although they are in fact open systems, the internal combustion engines are modelled as heat engines, with their corresponding cycles (Otto, Diesel or Brayton). This is done using the steady flow assumption: as in every cycle enters the same amount of mixture as hot gas is expelled, it can be treated as if the same fluid were making the cycle continuously, with just the heat being discarded.--88.18.219.135 (talk) 10:34, 9 May 2009 (UTC)

Internal combustion engines are a type of heat engines, because even though the way heat is generated is different, they subsequently do convert heat into work. A good definition of heat engines should therefore also include open systems and internal combustion engines. I think the definition below covers internal combustion engines (the working substance passes only once through the working body in an internal combustion engine). Teep111

In thermodynamics, a heat engine is a system that performs the conversion of heat energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates heat that brings the working substance in the high temperature state. The working substance generates work in the "working body" of the engine while transferring heat to the colder "sink" until it reaches a low temperature state. During this process some of the heat is converted into work by exploiting the properties of the working substance. The working substance can be any system with a non-zero heat capacity, but it usually is a gas or liquid. — Preceding unsigned comment added by Teep111 (talk • contribs) 23:36, 20 January 2011 (UTC)

Everyday examples

The article says: "Examples of everyday heat engines include the steam engine, the diesel engine, and the gasoline (petrol) engine in an automobile." I strongly disagree with the statement that the internal combustion engine is a good example of a heat engine. The main reason the cylinder in an IC engine moves is because the chemical reaction increases the number of molecules of gas, which increases the pressure as described by the ideal gas law PV = nRT. The higher temperature resulting from combustion also increases the pressure, but this increase can only be on the order of two-fold or three-fold (at most). The increase in the number of moles of gas due to the combustion reaction is over over ten-fold. Thomas.Hedden (talk) 21:53, 2 November 2013 (UTC)

Incorrect or Deceptive use of "Sink"

The use of the term "sink" (or as the currently linked article more technically puts it, "heat sink") seems to me to be a conflation of 'useful' with 'non-useful' or 'excess' heat. I suggest removing this term to reduce probable confusion resulting. I will do so now, but feel free to redact with pending argument. Typenolies (talk) 18:49, 21 September 2015 (UTC)

It's used perfectly correctly. The link is wrong though, and I've relinked it. The term 'sink' is already used in the new linked-to article.GliderMaven (talk)

I disagree that "sink" or "thermal reservoir" are being used correctly, because they don't adequately convey the purpose or desired action of a heat engine, which is to convert the useful energy in the heat, not transfer the heat itself. I won't revert back, but I'd like the statement to be replaced with a more purposeful summary of where the heat goes and what it's trying to accomplish.Typenolies (talk) 04:16, 11 October 2015 (UTC)

Sterling cycle and Malone engine

Do sterling cycles really require the fluid to be a gas? I ask because I've come across an obscure cycle that is described as being like a sterling cycle but using liquid rather than gas. see http://www.douglas-self.com/MUSEUM/POWER/maloneliquid/maloneliquid.htm thermodynamic cycles are described using cycles of thermodynamic processes so in much same way as a sterling is still a sterling if it runs on air or helium. So as long as the processes remain the same the choice of fluid shouldn't prevent the malone being considered a sterling. — Preceding unsigned comment added by 82.47.140.47 (talk) 19:53, 28 August 2012 (UTC)

Efficiency

In the overview, the maximum theoretical efficiency is quoted as being the "temperature difference between the hot and cold ends divided by the temperature at the hot end...". This is incorrect. The correct COP (found elsewhere in wikipedia) is given by T (hot)/(T (hot)-T (cold)) and the efficiency is given by W/Q (hot)=(Q (hot)-Q (cold))/Q (hot) (source: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heaeng.html) 76.198.38.250 (talk)

Heat transfer

Added lede part and image to heat transfer, here. Prokaryotes (talk) 20:09, 6 April 2014 (UTC)

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Need an article on Carnot Efficiency

The tag Carnot efficiency redirects here, but since Carnot efficiency is so central to many applications other than engines, it would probably be useful to make this a separate article. Geoffrey.landis (talk) 14:44, 22 June 2020 (UTC)

...wait, I realized that this isn't even the best article to redirect Carnot efficiency to-- there is an article Carnot's theorem (thermodynamics) which is specifically about Carnot efficiency. And there are four other article which would also be better than this one: Thermal efficiency, Carnot heat engine, Carnot cycle and Second law of thermodynamics. Geoffrey.landis (talk) 14:51, 22 June 2020 (UTC)

For 10 days in February 2007 the redirect was aimed at Exergy efficiency so that makes five! Dolphin (t) 22:21, 22 June 2020 (UTC)

Additional Phase-Change Cycle:

Comment: missing Shape Memory Alloy for solid-solid phase such as Nitinol engine - User:Twingy